SQL查询计数()多个表

我有一个表与其他表有几个很多的关系.让我们说主桌是一个人,其他桌子代表宠物,汽车和孩子.我想要一个查询,返回该人的详细信息,宠物,汽车和儿童的数量,例如

Person.Name   Count(cars) Count(children) Count(pets)

John Smith    3           2               4
Bob Brown     1           3               0

这样做最好的方法是什么？

解决方法

WITH count_cars AS (
    SELECT t.person_id
           COUNT(*) num_cars
      FROM CARS c
  GROUP BY t.person_id),count_children AS (
    SELECT t.person_id
           COUNT(*) num_children
      FROM CHILDREN c
  GROUP BY t.person_id),count_pets AS (
    SELECT p.person_id
           COUNT(*) num_pets
      FROM PETS p
  GROUP BY p.person_id)
   SELECT t.name,NVL(cars.num_cars,0) 'Count(cars)',NVL(children.num_children,0) 'Count(children)',NVL(pets.num_pets,0) 'Count(pets)'
     FROM PERSONS t
LEFT JOIN count_cars cars ON cars.person_id = t.person_id
LEFT JOIN count_children children ON children.person_id = t.person_id
LEFT JOIN count_pets pets ON pets.person_id = t.person_id

使用内联视图：

SELECT t.name,0) 'Count(pets)'
     FROM PERSONS t
LEFT JOIN (SELECT t.person_id
                  COUNT(*) num_cars
             FROM CARS c
         GROUP BY t.person_id) cars ON cars.person_id = t.person_id
LEFT JOIN (SELECT t.person_id
                  COUNT(*) num_children
             FROM CHILDREN c
         GROUP BY t.person_id) children ON children.person_id = t.person_id
LEFT JOIN (SELECT p.person_id
                  COUNT(*) num_pets
             FROM PETS p
         GROUP BY p.person_id) pets ON pets.person_id = t.person_id

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